Tristan Louis has an excellent analysis up on his site comparing Yahoo and Google (and Technorati too). His findings are quite interesting and mesh with my ad hoc searching for blogs in both Yahoo and Google. I urge you to go to his site and read his work, but here are the salient points:
# Yahoo! generally does a better job at indexing the blogosphere than Google does. We know they have been working hard to improve their index and here’s proof that they are getting results \ # Even if Google is the one with the motto about not doing evil, Yahoo! seems to be the one interested in giving equal opportunity to the little guy: smaller blogs seem to have a better chance of being recognized by Yahoo! than they do of being recognized by Google.
Thus the reason for a higher rank for this unknown blog in Yahoo than in Google.